1. Field of the Invention
The invention relates to a hydraulic exerciser, more particularly to a hydraulic exerciser which is provided with a pair of reciprocating hydraulic cylinders.
2. Description of the Related Art
U.S. Pat. No. 5,236,407 discloses a hydraulic exerciser which is provided with a pair of reciprocating hydraulic cylinders. As shown in FIG. 1, the hydraulic exerciser 1 comprises a base 13 and a pair of driven units 11, 12 mounted pivotably on the base 13 at one end. An elongated hollow support 14 is secured on the base 13 and extends between the driven units 11, 12.
Referring to FIGS. 1 and 2, each of a pair of hydraulic cylinders 2 has a cylinder body 20, a piston 24 disposed movably inside the cylinder body 20, and a piston rod 26 which has a first end connected to the piston 24 and a second end which extends out of the cylinder body 20 and which is connected to a respective one of the driven units 2.
A metal tubular connector 3 is secured on the support 14 and extends between the driven units 11, 12. The tubular connector 3 has two ends that extend through opposite ends of the support 14 so as to permit mounting of the cylinder bodies 20 of the hydraulic cylinders 2 thereon. The tubular connector 3 has a flexible rubber tube 31 provided therein. The tubular connector 3 is further provided with a threaded radial bore which receives the threaded shank of a rotary knob 32. The rotary knob 32 is operable in order to pinch a portion of the rubber tube 31 and regulate the flow of fluid therethrough.
A rigid tubular end piece 4 is provided at each end of the rubber tube 31. Each tubular end piece 4 has a tapered portion 41 which is fitted in the respective end of the rubber tube 31 and which causes the respective end of the rubber tube 31 to expand and press tightly against the tubular connector 3 in order to seal the gap between the rubber tube 31 and the tubular connector 3. Each of the tubular end pieces 4 defines a fluid path 42 and is provided with a radial hole 43 which is communicated with the fluid path 42. A cap 34 is mounted threadedly on each end of the tubular connector 3 and is used to retain the end pieces 4 and the rubber tube 31 inside the tubular connector 3. A clearance 33 is formed between a portion of the tubular end piece 4 and the tubular connector 3. One of the caps 5 is provided with a fluid inlet 35. The fluid inlet 35 is adapted to be connected to a hydraulic fluid supply (A) which is used to remove or supply hydraulic fluid to the rubber tube 31.
Referring to FIGS. 2 and 3, the cylinder body 20 of each hydraulic cylinder 2 has one end which is provided with a plug 22. The plug 22 is formed with a ring connector 221 that defines a through hole 23. The plug 22 is further provided with an axial fluid hole 21 which communicates the interior of the cylinder body 20 with the through hole 23. The plug 22 cooperates with the cylinder body 20 and the piston 24 so as to define a volume variable fluid chamber 25 which is filled with hydraulic fluid. The ring connectors 221 of the hydraulic cylinders 2 are sleeved on a respective end of the tubular connector 3, thereby mounting pivotably the hydraulic cylinders 2 on the tubular connector 3. Each end of the tubular connector 3 is further provided with an annular peripheral groove 37 and a fluid hole 36 that is formed in the peripheral groove 37. The peripheral groove 37 is aligned with the fluid hole 21 of the plug 22 and permits the flow of hydraulic fluid from the fluid chamber 25 to the clearance 33 via the fluid hole 36, and vice versa.
Whenever a downward pushing force is applied on one of the driven units 11, 12, the piston 24 of the corresponding hydraulic cylinder 2 moves downward, thereby causing the hydraulic fluid inside the fluid chamber 25 to flow through the fluid hole 21, the peripheral groove 37, the fluid hole 36, the clearance 33, the radial hole 43 of one of the tubular end pieces 4, the fluid path 42 and into the rubber tube 31. Fluid inside the rubber tube 31 then flows through the fluid path 42 of the other tubular end piece 4, the radial hole 43, the clearance 33, the fluid hole 36, the peripheral groove 37, the fluid hole 21 and into the fluid chamber 25 of the other hydraulic cylinder 2. The entry of hydraulic fluid in the fluid chamber 25 causes upward movement of the piston 24 in the other hydraulic cylinder 2, thereby resulting in upward movement of the other one of the driven units 11, 12.
Some of the drawbacks of the above described hydraulic exerciser 1 are as follows:
1. The ring connectors 221 mount pivotably the hydraulic cylinders 2 on the tubular connector 3. In order to ensure proper pivoting movement of the hydraulic cylinders 2 while preventing leakage of high temperature, high pressure hydraulic fluid, a high degree of precision is needed when forming the ring connectors 221 and the tubular connector 3.
2. The rotary knob 32 and the rubber tube 31 constitute a regulator for varying the resistance offered by the hydraulic cylinders 2 to movement of the driven units 11, 12. It is noted that the tip of the rotary knob 32 abuts a portion of the rubber tube 31 in order to pinch the latter. Due to the relatively large fluid pressure in the rubber tube 31, the tip of the rotary knob 32 can damage easily the rubber tube 31. In addition, the tubular end pieces 4 cause the two ends of the rubber tube 31 to expand and press tightly against the tubular connector 3 in order to seal the gap between the rubber tube 31 and the tubular connector 3. Damage to the rubber tube 31 easily occurs because the two ends thereof are maintained in a stretched state.
3. The hydraulic exerciser 1 has numerous components, thereby complicating the manufacture and assembly thereof.